/*
 * QR Code generator library (C)
 *
 * Copyright (c) Project Nayuki. (MIT License)
 * https://www.nayuki.io/page/qr-code-generator-library
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * - The above copyright notice and this permission notice shall be included in
 *   all copies or substantial portions of the Software.
 * - The Software is provided "as is", without warranty of any kind, express or
 *   implied, including but not limited to the warranties of merchantability,
 *   fitness for a particular purpose and noninfringement. In no event shall the
 *   authors or copyright holders be liable for any claim, damages or other
 *   liability, whether in an action of contract, tort or otherwise, arising from,
 *   out of or in connection with the Software or the use or other dealings in the
 *   Software.
 */

#include <assert.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include "qrcodegen.h"

#ifndef QRCODEGEN_TEST
    #define testable    static /* Keep functions private */
#else
    #define testable           /* Expose private functions */
#endif


/*---- Forward declarations for private functions ----*/

/* Regarding all public and private functions defined in this source file: */
/* - They require all pointer/array arguments to be not null unless the array length is zero. */
/* - They only read input scalar/array arguments, write to output pointer/array */
/*   arguments, and return scalar values; they are "pure" functions. */
/* - They don't read mutable global variables or write to any global variables. */
/* - They don't perform I/O, read the clock, print to console, etc. */
/* - They allocate a small and constant amount of stack memory. */
/* - They don't allocate or free any memory on the heap. */
/* - They don't recurse or mutually recurse. All the code */
/*   could be inlined into the top-level public functions. */
/* - They run in at most quadratic time with respect to input arguments. */
/*   Most functions run in linear time, and some in constant time. */
/*   There are no unbounded loops or non-obvious termination conditions. */
/* - They are completely thread-safe if the caller does not give the */
/*   same writable buffer to concurrent calls to these functions. */

testable void appendBitsToBuffer( unsigned int val,
                                  int numBits,
                                  uint8_t buffer[],
                                  int * bitLen );

testable void addEccAndInterleave( uint8_t data[],
                                   int version,
                                   enum qrcodegen_Ecc ecl,
                                   uint8_t result[] );
testable int getNumDataCodewords( int version,
                                  enum qrcodegen_Ecc ecl );
testable int getNumRawDataModules( int ver );

testable void reedSolomonComputeDivisor( int degree,
                                         uint8_t result[] );
testable void reedSolomonComputeRemainder( const uint8_t data[],
                                           int dataLen,
                                           const uint8_t generator[],
                                           int degree,
                                           uint8_t result[] );
testable uint8_t reedSolomonMultiply( uint8_t x,
                                      uint8_t y );

testable void initializeFunctionModules( int version,
                                         uint8_t qrcode[] );
static void drawWhiteFunctionModules( uint8_t qrcode[],
                                      int version );
static void drawFormatBits( enum qrcodegen_Ecc ecl,
                            enum qrcodegen_Mask mask,
                            uint8_t qrcode[] );
testable int getAlignmentPatternPositions( int version,
                                           uint8_t result[ 7 ] );
static void fillRectangle( int left,
                           int top,
                           int width,
                           int height,
                           uint8_t qrcode[] );

static void drawCodewords( const uint8_t data[],
                           int dataLen,
                           uint8_t qrcode[] );
static void applyMask( const uint8_t functionModules[],
                       uint8_t qrcode[],
                       enum qrcodegen_Mask mask );
static long getPenaltyScore( const uint8_t qrcode[] );
static int finderPenaltyCountPatterns( const int runHistory[ 7 ],
                                       int qrsize );
static int finderPenaltyTerminateAndCount( bool currentRunColor,
                                           int currentRunLength,
                                           int runHistory[ 7 ],
                                           int qrsize );
static void finderPenaltyAddHistory( int currentRunLength,
                                     int runHistory[ 7 ] );

testable bool getModule( const uint8_t qrcode[],
                         int x,
                         int y );
testable void setModule( uint8_t qrcode[],
                         int x,
                         int y,
                         bool isBlack );
testable void setModuleBounded( uint8_t qrcode[],
                                int x,
                                int y,
                                bool isBlack );
static bool getBit( int x,
                    int i );

testable int calcSegmentBitLength( enum qrcodegen_Mode mode,
                                   size_t numChars );
testable int getTotalBits( const struct qrcodegen_Segment segs[],
                           size_t len,
                           int version );
static int numCharCountBits( enum qrcodegen_Mode mode,
                             int version );



/*---- Private tables of constants ----*/

/* The set of all legal characters in alphanumeric mode, where each character */
/* value maps to the index in the string. For checking text and encoding segments. */
static const char * ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";

/* For generating error correction codes. */
testable const int8_t ECC_CODEWORDS_PER_BLOCK[ 4 ][ 41 ] =
{
    /* Version: (note that index 0 is for padding, and is set to an illegal value) */
    /*0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level */
    { -1, 7,  10, 15, 20, 26, 18, 20, 24, 30, 18, 20, 24, 26, 30, 22, 24, 28, 30, 28, 28, 28, 28, 30, 30, 26, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30 }, /* Low */
    { -1, 10, 16, 26, 18, 24, 16, 18, 22, 22, 26, 30, 22, 22, 24, 24, 28, 28, 26, 26, 26, 26, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28 }, /* Medium */
    { -1, 13, 22, 18, 26, 18, 24, 18, 22, 20, 24, 28, 26, 24, 20, 30, 24, 28, 28, 26, 30, 28, 30, 30, 30, 30, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30 }, /* Quartile */
    { -1, 17, 28, 22, 16, 22, 28, 26, 26, 24, 28, 24, 28, 22, 24, 24, 30, 28, 28, 26, 28, 30, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30 }, /* High */
};

#define qrcodegen_REED_SOLOMON_DEGREE_MAX    30 /* Based on the table above */

/* For generating error correction codes. */
testable const int8_t NUM_ERROR_CORRECTION_BLOCKS[ 4 ][ 41 ] =
{
    /* Version: (note that index 0 is for padding, and is set to an illegal value) */
    /*0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level */
    { -1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 4, 4,  4,  4,  4,  6,  6,  6,  6,  7,  8,  8,  9,  9,  10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25 }, /* Low */
    { -1, 1, 1, 1, 2, 2, 4, 4, 4, 5, 5, 5,  8,  9,  9,  10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49 }, /* Medium */
    { -1, 1, 1, 2, 2, 4, 4, 6, 6, 8, 8, 8,  10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68 }, /* Quartile */
    { -1, 1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81 }, /* High */
};

/* For automatic mask pattern selection. */
static const int PENALTY_N1 = 3;
static const int PENALTY_N2 = 3;
static const int PENALTY_N3 = 40;
static const int PENALTY_N4 = 10;



/*---- High-level QR Code encoding functions ----*/

/* Public function - see documentation comment in header file. */
bool qrcodegen_encodeText( const char * text,
                           uint8_t tempBuffer[],
                           uint8_t qrcode[],
                           enum qrcodegen_Ecc ecl,
                           int minVersion,
                           int maxVersion,
                           enum qrcodegen_Mask mask,
                           bool boostEcl )
{
    size_t textLen = strlen( text );

    if( textLen == 0 )
    {
        return qrcodegen_encodeSegmentsAdvanced( NULL, 0, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode );
    }

    size_t bufLen = ( size_t ) qrcodegen_BUFFER_LEN_FOR_VERSION( maxVersion );

    struct qrcodegen_Segment seg;

    if( qrcodegen_isNumeric( text ) )
    {
        if( qrcodegen_calcSegmentBufferSize( qrcodegen_Mode_NUMERIC, textLen ) > bufLen )
        {
            goto fail;
        }

        seg = qrcodegen_makeNumeric( text, tempBuffer );
    }
    else if( qrcodegen_isAlphanumeric( text ) )
    {
        if( qrcodegen_calcSegmentBufferSize( qrcodegen_Mode_ALPHANUMERIC, textLen ) > bufLen )
        {
            goto fail;
        }

        seg = qrcodegen_makeAlphanumeric( text, tempBuffer );
    }
    else
    {
        if( textLen > bufLen )
        {
            goto fail;
        }

        for( size_t i = 0; i < textLen; i++ )
        {
            tempBuffer[ i ] = ( uint8_t ) text[ i ];
        }

        seg.mode = qrcodegen_Mode_BYTE;
        seg.bitLength = calcSegmentBitLength( seg.mode, textLen );

        if( seg.bitLength == -1 )
        {
            goto fail;
        }

        seg.numChars = ( int ) textLen;
        seg.data = tempBuffer;
    }

    return qrcodegen_encodeSegmentsAdvanced( &seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode );

fail:
    qrcode[ 0 ] = 0; /* Set size to invalid value for safety */
    return false;
}


/* Public function - see documentation comment in header file. */
bool qrcodegen_encodeBinary( uint8_t dataAndTemp[],
                             size_t dataLen,
                             uint8_t qrcode[],
                             enum qrcodegen_Ecc ecl,
                             int minVersion,
                             int maxVersion,
                             enum qrcodegen_Mask mask,
                             bool boostEcl )
{
    struct qrcodegen_Segment seg;

    seg.mode = qrcodegen_Mode_BYTE;
    seg.bitLength = calcSegmentBitLength( seg.mode, dataLen );

    if( seg.bitLength == -1 )
    {
        qrcode[ 0 ] = 0; /* Set size to invalid value for safety */
        return false;
    }

    seg.numChars = ( int ) dataLen;
    seg.data = dataAndTemp;
    return qrcodegen_encodeSegmentsAdvanced( &seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, dataAndTemp, qrcode );
}


/* Appends the given number of low-order bits of the given value to the given byte-based */
/* bit buffer, increasing the bit length. Requires 0 <= numBits <= 16 and val < 2^numBits. */
testable void appendBitsToBuffer( unsigned int val,
                                  int numBits,
                                  uint8_t buffer[],
                                  int * bitLen )
{
    assert( 0 <= numBits && numBits <= 16 && ( unsigned long ) val >> numBits == 0 );

    for( int i = numBits - 1; i >= 0; i--, ( *bitLen )++ )
    {
        buffer[ *bitLen >> 3 ] |= ( ( val >> i ) & 1 ) << ( 7 - ( *bitLen & 7 ) );
    }
}



/*---- Low-level QR Code encoding functions ----*/

/* Public function - see documentation comment in header file. */
bool qrcodegen_encodeSegments( const struct qrcodegen_Segment segs[],
                               size_t len,
                               enum qrcodegen_Ecc ecl,
                               uint8_t tempBuffer[],
                               uint8_t qrcode[] )
{
    return qrcodegen_encodeSegmentsAdvanced( segs, len, ecl,
                                             qrcodegen_VERSION_MIN, qrcodegen_VERSION_MAX, qrcodegen_Mask_AUTO, true, tempBuffer, qrcode );
}


/* Public function - see documentation comment in header file. */
bool qrcodegen_encodeSegmentsAdvanced( const struct qrcodegen_Segment segs[],
                                       size_t len,
                                       enum qrcodegen_Ecc ecl,
                                       int minVersion,
                                       int maxVersion,
                                       enum qrcodegen_Mask mask,
                                       bool boostEcl,
                                       uint8_t tempBuffer[],
                                       uint8_t qrcode[] )
{
    assert( segs != NULL || len == 0 );
    assert( qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX );
    assert( 0 <= ( int ) ecl && ( int ) ecl <= 3 && -1 <= ( int ) mask && ( int ) mask <= 7 );

    /* Find the minimal version number to use */
    int version, dataUsedBits;

    for( version = minVersion; ; version++ )
    {
        int dataCapacityBits = getNumDataCodewords( version, ecl ) * 8; /* Number of data bits available */
        dataUsedBits = getTotalBits( segs, len, version );

        if( ( dataUsedBits != -1 ) && ( dataUsedBits <= dataCapacityBits ) )
        {
            break; /* This version number is found to be suitable */
        }

        if( version >= maxVersion ) /* All versions in the range could not fit the given data */
        {
            qrcode[ 0 ] = 0;        /* Set size to invalid value for safety */
            return false;
        }
    }

    assert( dataUsedBits != -1 );

    /* Increase the error correction level while the data still fits in the current version number */
    for( int i = ( int ) qrcodegen_Ecc_MEDIUM; i <= ( int ) qrcodegen_Ecc_HIGH; i++ ) /* From low to high */
    {
        if( boostEcl && ( dataUsedBits <= getNumDataCodewords( version, ( enum qrcodegen_Ecc ) i ) * 8 ) )
        {
            ecl = ( enum qrcodegen_Ecc ) i;
        }
    }

    /* Concatenate all segments to create the data bit string */
    memset( qrcode, 0, ( size_t ) qrcodegen_BUFFER_LEN_FOR_VERSION( version ) * sizeof( qrcode[ 0 ] ) );
    int bitLen = 0;

    for( size_t i = 0; i < len; i++ )
    {
        const struct qrcodegen_Segment * seg = &segs[ i ];
        appendBitsToBuffer( ( unsigned int ) seg->mode, 4, qrcode, &bitLen );
        appendBitsToBuffer( ( unsigned int ) seg->numChars, numCharCountBits( seg->mode, version ), qrcode, &bitLen );

        for( int j = 0; j < seg->bitLength; j++ )
        {
            int bit = ( seg->data[ j >> 3 ] >> ( 7 - ( j & 7 ) ) ) & 1;
            appendBitsToBuffer( ( unsigned int ) bit, 1, qrcode, &bitLen );
        }
    }

    assert( bitLen == dataUsedBits );

    /* Add terminator and pad up to a byte if applicable */
    int dataCapacityBits = getNumDataCodewords( version, ecl ) * 8;
    assert( bitLen <= dataCapacityBits );
    int terminatorBits = dataCapacityBits - bitLen;

    if( terminatorBits > 4 )
    {
        terminatorBits = 4;
    }

    appendBitsToBuffer( 0, terminatorBits, qrcode, &bitLen );
    appendBitsToBuffer( 0, ( 8 - bitLen % 8 ) % 8, qrcode, &bitLen );
    assert( bitLen % 8 == 0 );

    /* Pad with alternating bytes until data capacity is reached */
    for( uint8_t padByte = 0xEC; bitLen < dataCapacityBits; padByte ^= 0xEC ^ 0x11 )
    {
        appendBitsToBuffer( padByte, 8, qrcode, &bitLen );
    }

    /* Draw function and data codeword modules */
    addEccAndInterleave( qrcode, version, ecl, tempBuffer );
    initializeFunctionModules( version, qrcode );
    drawCodewords( tempBuffer, getNumRawDataModules( version ) / 8, qrcode );
    drawWhiteFunctionModules( qrcode, version );
    initializeFunctionModules( version, tempBuffer );

    /* Handle masking */
    if( mask == qrcodegen_Mask_AUTO ) /* Automatically choose best mask */
    {
        long minPenalty = LONG_MAX;

        for( int i = 0; i < 8; i++ )
        {
            enum qrcodegen_Mask msk = ( enum qrcodegen_Mask ) i;
            applyMask( tempBuffer, qrcode, msk );
            drawFormatBits( ecl, msk, qrcode );
            long penalty = getPenaltyScore( qrcode );

            if( penalty < minPenalty )
            {
                mask = msk;
                minPenalty = penalty;
            }

            applyMask( tempBuffer, qrcode, msk ); /* Undoes the mask due to XOR */
        }
    }

    assert( 0 <= ( int ) mask && ( int ) mask <= 7 );
    applyMask( tempBuffer, qrcode, mask );
    drawFormatBits( ecl, mask, qrcode );
    return true;
}



/*---- Error correction code generation functions ----*/

/* Appends error correction bytes to each block of the given data array, then interleaves */
/* bytes from the blocks and stores them in the result array. data[0 : dataLen] contains */
/* the input data. data[dataLen : rawCodewords] is used as a temporary work area and will */
/* be clobbered by this function. The final answer is stored in result[0 : rawCodewords]. */
testable void addEccAndInterleave( uint8_t data[],
                                   int version,
                                   enum qrcodegen_Ecc ecl,
                                   uint8_t result[] )
{
    /* Calculate parameter numbers */
    assert( 0 <= ( int ) ecl && ( int ) ecl < 4 && qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX );
    int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[ ( int ) ecl ][ version ];
    int blockEccLen = ECC_CODEWORDS_PER_BLOCK[ ( int ) ecl ][ version ];
    int rawCodewords = getNumRawDataModules( version ) / 8;
    int dataLen = getNumDataCodewords( version, ecl );
    int numShortBlocks = numBlocks - rawCodewords % numBlocks;
    int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen;

    /* Split data into blocks, calculate ECC, and interleave */
    /* (not concatenate) the bytes into a single sequence */
    uint8_t rsdiv[ qrcodegen_REED_SOLOMON_DEGREE_MAX ];
    reedSolomonComputeDivisor( blockEccLen, rsdiv );
    const uint8_t * dat = data;

    for( int i = 0; i < numBlocks; i++ )
    {
        int datLen = shortBlockDataLen + ( i < numShortBlocks ? 0 : 1 );
        uint8_t * ecc = &data[ dataLen ]; /* Temporary storage */
        reedSolomonComputeRemainder( dat, datLen, rsdiv, blockEccLen, ecc );

        for( int j = 0, k = i; j < datLen; j++, k += numBlocks ) /* Copy data */
        {
            if( j == shortBlockDataLen )
            {
                k -= numShortBlocks;
            }

            result[ k ] = dat[ j ];
        }

        for( int j = 0, k = dataLen + i; j < blockEccLen; j++, k += numBlocks ) /* Copy ECC */
        {
            result[ k ] = ecc[ j ];
        }

        dat += datLen;
    }
}


/* Returns the number of 8-bit codewords that can be used for storing data (not ECC), */
/* for the given version number and error correction level. The result is in the range [9, 2956]. */
testable int getNumDataCodewords( int version,
                                  enum qrcodegen_Ecc ecl )
{
    int v = version, e = ( int ) ecl;

    assert( 0 <= e && e < 4 );
    return getNumRawDataModules( v ) / 8
           - ECC_CODEWORDS_PER_BLOCK[ e ][ v ]
           * NUM_ERROR_CORRECTION_BLOCKS[ e ][ v ];
}


/* Returns the number of data bits that can be stored in a QR Code of the given version number, after */
/* all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8. */
/* The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table. */
testable int getNumRawDataModules( int ver )
{
    assert( qrcodegen_VERSION_MIN <= ver && ver <= qrcodegen_VERSION_MAX );
    int result = ( 16 * ver + 128 ) * ver + 64;

    if( ver >= 2 )
    {
        int numAlign = ver / 7 + 2;
        result -= ( 25 * numAlign - 10 ) * numAlign - 55;

        if( ver >= 7 )
        {
            result -= 36;
        }
    }

    assert( 208 <= result && result <= 29648 );
    return result;
}



/*---- Reed-Solomon ECC generator functions ----*/

/* Computes a Reed-Solomon ECC generator polynomial for the given degree, storing in result[0 : degree]. */
/* This could be implemented as a lookup table over all possible parameter values, instead of as an algorithm. */
testable void reedSolomonComputeDivisor( int degree,
                                         uint8_t result[] )
{
    assert( 1 <= degree && degree <= qrcodegen_REED_SOLOMON_DEGREE_MAX );
    /* Polynomial coefficients are stored from highest to lowest power, excluding the leading term which is always 1. */
    /* For example the polynomial x^3 + 255x^2 + 8x + 93 is stored as the uint8 array {255, 8, 93}. */
    memset( result, 0, ( size_t ) degree * sizeof( result[ 0 ] ) );
    result[ degree - 1 ] = 1; /* Start off with the monomial x^0 */

    /* Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}), */
    /* drop the highest monomial term which is always 1x^degree. */
    /* Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D). */
    uint8_t root = 1;

    for( int i = 0; i < degree; i++ )
    {
        /* Multiply the current product by (x - r^i) */
        for( int j = 0; j < degree; j++ )
        {
            result[ j ] = reedSolomonMultiply( result[ j ], root );

            if( j + 1 < degree )
            {
                result[ j ] ^= result[ j + 1 ];
            }
        }

        root = reedSolomonMultiply( root, 0x02 );
    }
}


/* Computes the Reed-Solomon error correction codeword for the given data and divisor polynomials. */
/* The remainder when data[0 : dataLen] is divided by divisor[0 : degree] is stored in result[0 : degree]. */
/* All polynomials are in big endian, and the generator has an implicit leading 1 term. */
testable void reedSolomonComputeRemainder( const uint8_t data[],
                                           int dataLen,
                                           const uint8_t generator[],
                                           int degree,
                                           uint8_t result[] )
{
    assert( 1 <= degree && degree <= qrcodegen_REED_SOLOMON_DEGREE_MAX );
    memset( result, 0, ( size_t ) degree * sizeof( result[ 0 ] ) );

    for( int i = 0; i < dataLen; i++ ) /* Polynomial division */
    {
        uint8_t factor = data[ i ] ^ result[ 0 ];
        memmove( &result[ 0 ], &result[ 1 ], ( size_t ) ( degree - 1 ) * sizeof( result[ 0 ] ) );
        result[ degree - 1 ] = 0;

        for( int j = 0; j < degree; j++ )
        {
            result[ j ] ^= reedSolomonMultiply( generator[ j ], factor );
        }
    }
}

#undef qrcodegen_REED_SOLOMON_DEGREE_MAX


/* Returns the product of the two given field elements modulo GF(2^8/0x11D). */
/* All inputs are valid. This could be implemented as a 256*256 lookup table. */
testable uint8_t reedSolomonMultiply( uint8_t x,
                                      uint8_t y )
{
    /* Russian peasant multiplication */
    uint8_t z = 0;

    for( int i = 7; i >= 0; i-- )
    {
        z = ( uint8_t ) ( ( z << 1 ) ^ ( ( z >> 7 ) * 0x11D ) );
        z ^= ( ( y >> i ) & 1 ) * x;
    }

    return z;
}



/*---- Drawing function modules ----*/

/* Clears the given QR Code grid with white modules for the given */
/* version's size, then marks every function module as black. */
testable void initializeFunctionModules( int version,
                                         uint8_t qrcode[] )
{
    /* Initialize QR Code */
    int qrsize = version * 4 + 17;

    memset( qrcode, 0, ( size_t ) ( ( qrsize * qrsize + 7 ) / 8 + 1 ) * sizeof( qrcode[ 0 ] ) );
    qrcode[ 0 ] = ( uint8_t ) qrsize;

    /* Fill horizontal and vertical timing patterns */
    fillRectangle( 6, 0, 1, qrsize, qrcode );
    fillRectangle( 0, 6, qrsize, 1, qrcode );

    /* Fill 3 finder patterns (all corners except bottom right) and format bits */
    fillRectangle( 0, 0, 9, 9, qrcode );
    fillRectangle( qrsize - 8, 0, 8, 9, qrcode );
    fillRectangle( 0, qrsize - 8, 9, 8, qrcode );

    /* Fill numerous alignment patterns */
    uint8_t alignPatPos[ 7 ];
    int numAlign = getAlignmentPatternPositions( version, alignPatPos );

    for( int i = 0; i < numAlign; i++ )
    {
        for( int j = 0; j < numAlign; j++ )
        {
            /* Don't draw on the three finder corners */
            if( !( ( ( i == 0 ) && ( j == 0 ) ) || ( ( i == 0 ) && ( j == numAlign - 1 ) ) || ( ( i == numAlign - 1 ) && ( j == 0 ) ) ) )
            {
                fillRectangle( alignPatPos[ i ] - 2, alignPatPos[ j ] - 2, 5, 5, qrcode );
            }
        }
    }

    /* Fill version blocks */
    if( version >= 7 )
    {
        fillRectangle( qrsize - 11, 0, 3, 6, qrcode );
        fillRectangle( 0, qrsize - 11, 6, 3, qrcode );
    }
}


/* Draws white function modules and possibly some black modules onto the given QR Code, without changing */
/* non-function modules. This does not draw the format bits. This requires all function modules to be previously */
/* marked black (namely by initializeFunctionModules()), because this may skip redrawing black function modules. */
static void drawWhiteFunctionModules( uint8_t qrcode[],
                                      int version )
{
    /* Draw horizontal and vertical timing patterns */
    int qrsize = qrcodegen_getSize( qrcode );

    for( int i = 7; i < qrsize - 7; i += 2 )
    {
        setModule( qrcode, 6, i, false );
        setModule( qrcode, i, 6, false );
    }

    /* Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules) */
    for( int dy = -4; dy <= 4; dy++ )
    {
        for( int dx = -4; dx <= 4; dx++ )
        {
            int dist = abs( dx );

            if( abs( dy ) > dist )
            {
                dist = abs( dy );
            }

            if( ( dist == 2 ) || ( dist == 4 ) )
            {
                setModuleBounded( qrcode, 3 + dx, 3 + dy, false );
                setModuleBounded( qrcode, qrsize - 4 + dx, 3 + dy, false );
                setModuleBounded( qrcode, 3 + dx, qrsize - 4 + dy, false );
            }
        }
    }

    /* Draw numerous alignment patterns */
    uint8_t alignPatPos[ 7 ];
    int numAlign = getAlignmentPatternPositions( version, alignPatPos );

    for( int i = 0; i < numAlign; i++ )
    {
        for( int j = 0; j < numAlign; j++ )
        {
            if( ( ( i == 0 ) && ( j == 0 ) ) || ( ( i == 0 ) && ( j == numAlign - 1 ) ) || ( ( i == numAlign - 1 ) && ( j == 0 ) ) )
            {
                continue; /* Don't draw on the three finder corners */
            }

            for( int dy = -1; dy <= 1; dy++ )
            {
                for( int dx = -1; dx <= 1; dx++ )
                {
                    setModule( qrcode, alignPatPos[ i ] + dx, alignPatPos[ j ] + dy, dx == 0 && dy == 0 );
                }
            }
        }
    }

    /* Draw version blocks */
    if( version >= 7 )
    {
        /* Calculate error correction code and pack bits */
        int rem = version; /* version is uint6, in the range [7, 40] */

        for( int i = 0; i < 12; i++ )
        {
            rem = ( rem << 1 ) ^ ( ( rem >> 11 ) * 0x1F25 );
        }

        long bits = ( long ) version << 12 | rem; /* uint18 */
        assert( bits >> 18 == 0 );

        /* Draw two copies */
        for( int i = 0; i < 6; i++ )
        {
            for( int j = 0; j < 3; j++ )
            {
                int k = qrsize - 11 + j;
                setModule( qrcode, k, i, ( bits & 1 ) != 0 );
                setModule( qrcode, i, k, ( bits & 1 ) != 0 );
                bits >>= 1;
            }
        }
    }
}


/* Draws two copies of the format bits (with its own error correction code) based */
/* on the given mask and error correction level. This always draws all modules of */
/* the format bits, unlike drawWhiteFunctionModules() which might skip black modules. */
static void drawFormatBits( enum qrcodegen_Ecc ecl,
                            enum qrcodegen_Mask mask,
                            uint8_t qrcode[] )
{
    /* Calculate error correction code and pack bits */
    assert( 0 <= ( int ) mask && ( int ) mask <= 7 );
    static const int table[] = { 1, 0, 3, 2 };
    int data = table[ ( int ) ecl ] << 3 | ( int ) mask; /* errCorrLvl is uint2, mask is uint3 */
    int rem = data;

    for( int i = 0; i < 10; i++ )
    {
        rem = ( rem << 1 ) ^ ( ( rem >> 9 ) * 0x537 );
    }

    int bits = ( data << 10 | rem ) ^ 0x5412; /* uint15 */
    assert( bits >> 15 == 0 );

    /* Draw first copy */
    for( int i = 0; i <= 5; i++ )
    {
        setModule( qrcode, 8, i, getBit( bits, i ) );
    }

    setModule( qrcode, 8, 7, getBit( bits, 6 ) );
    setModule( qrcode, 8, 8, getBit( bits, 7 ) );
    setModule( qrcode, 7, 8, getBit( bits, 8 ) );

    for( int i = 9; i < 15; i++ )
    {
        setModule( qrcode, 14 - i, 8, getBit( bits, i ) );
    }

    /* Draw second copy */
    int qrsize = qrcodegen_getSize( qrcode );

    for( int i = 0; i < 8; i++ )
    {
        setModule( qrcode, qrsize - 1 - i, 8, getBit( bits, i ) );
    }

    for( int i = 8; i < 15; i++ )
    {
        setModule( qrcode, 8, qrsize - 15 + i, getBit( bits, i ) );
    }

    setModule( qrcode, 8, qrsize - 8, true ); /* Always black */
}


/* Calculates and stores an ascending list of positions of alignment patterns */
/* for this version number, returning the length of the list (in the range [0,7]). */
/* Each position is in the range [0,177), and are used on both the x and y axes. */
/* This could be implemented as lookup table of 40 variable-length lists of unsigned bytes. */
testable int getAlignmentPatternPositions( int version,
                                           uint8_t result[ 7 ] )
{
    if( version == 1 )
    {
        return 0;
    }

    int numAlign = version / 7 + 2;
    int step = ( version == 32 ) ? 26 :
               ( version * 4 + numAlign * 2 + 1 ) / ( numAlign * 2 - 2 ) * 2;

    for( int i = numAlign - 1, pos = version * 4 + 10; i >= 1; i--, pos -= step )
    {
        result[ i ] = ( uint8_t ) pos;
    }

    result[ 0 ] = 6;
    return numAlign;
}


/* Sets every pixel in the range [left : left + width] * [top : top + height] to black. */
static void fillRectangle( int left,
                           int top,
                           int width,
                           int height,
                           uint8_t qrcode[] )
{
    for( int dy = 0; dy < height; dy++ )
    {
        for( int dx = 0; dx < width; dx++ )
        {
            setModule( qrcode, left + dx, top + dy, true );
        }
    }
}



/*---- Drawing data modules and masking ----*/

/* Draws the raw codewords (including data and ECC) onto the given QR Code. This requires the initial state of */
/* the QR Code to be black at function modules and white at codeword modules (including unused remainder bits). */
static void drawCodewords( const uint8_t data[],
                           int dataLen,
                           uint8_t qrcode[] )
{
    int qrsize = qrcodegen_getSize( qrcode );
    int i = 0; /* Bit index into the data */

    /* Do the funny zigzag scan */
    for( int right = qrsize - 1; right >= 1; right -= 2 ) /* Index of right column in each column pair */
    {
        if( right == 6 )
        {
            right = 5;
        }

        for( int vert = 0; vert < qrsize; vert++ ) /* Vertical counter */
        {
            for( int j = 0; j < 2; j++ )
            {
                int x = right - j;                         /* Actual x coordinate */
                bool upward = ( ( right + 1 ) & 2 ) == 0;
                int y = upward ? qrsize - 1 - vert : vert; /* Actual y coordinate */

                if( !getModule( qrcode, x, y ) && ( i < dataLen * 8 ) )
                {
                    bool black = getBit( data[ i >> 3 ], 7 - ( i & 7 ) );
                    setModule( qrcode, x, y, black );
                    i++;
                }

                /* If this QR Code has any remainder bits (0 to 7), they were assigned as */
                /* 0/false/white by the constructor and are left unchanged by this method */
            }
        }
    }

    assert( i == dataLen * 8 );
}


/* XORs the codeword modules in this QR Code with the given mask pattern. */
/* The function modules must be marked and the codeword bits must be drawn */
/* before masking. Due to the arithmetic of XOR, calling applyMask() with */
/* the same mask value a second time will undo the mask. A final well-formed */
/* QR Code needs exactly one (not zero, two, etc.) mask applied. */
static void applyMask( const uint8_t functionModules[],
                       uint8_t qrcode[],
                       enum qrcodegen_Mask mask )
{
    assert( 0 <= ( int ) mask && ( int ) mask <= 7 ); /* Disallows qrcodegen_Mask_AUTO */
    int qrsize = qrcodegen_getSize( qrcode );

    for( int y = 0; y < qrsize; y++ )
    {
        for( int x = 0; x < qrsize; x++ )
        {
            if( getModule( functionModules, x, y ) )
            {
                continue;
            }

            bool invert;

            switch( ( int ) mask )
            {
                case 0:
                    invert = ( x + y ) % 2 == 0;
                    break;

                case 1:
                    invert = y % 2 == 0;
                    break;

                case 2:
                    invert = x % 3 == 0;
                    break;

                case 3:
                    invert = ( x + y ) % 3 == 0;
                    break;

                case 4:
                    invert = ( x / 3 + y / 2 ) % 2 == 0;
                    break;

                case 5:
                    invert = x * y % 2 + x * y % 3 == 0;
                    break;

                case 6:
                    invert = ( x * y % 2 + x * y % 3 ) % 2 == 0;
                    break;

                case 7:
                    invert = ( ( x + y ) % 2 + x * y % 3 ) % 2 == 0;
                    break;

                default:
                    assert( false );
                    return;
            }

            bool val = getModule( qrcode, x, y );
            setModule( qrcode, x, y, val ^ invert );
        }
    }
}


/* Calculates and returns the penalty score based on state of the given QR Code's current modules. */
/* This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score. */
static long getPenaltyScore( const uint8_t qrcode[] )
{
    int qrsize = qrcodegen_getSize( qrcode );
    long result = 0;

    /* Adjacent modules in row having same color, and finder-like patterns */
    for( int y = 0; y < qrsize; y++ )
    {
        bool runColor = false;
        int runX = 0;
        int runHistory[ 7 ] = { 0 };
        int padRun = qrsize; /* Add white border to initial run */

        for( int x = 0; x < qrsize; x++ )
        {
            if( getModule( qrcode, x, y ) == runColor )
            {
                runX++;

                if( runX == 5 )
                {
                    result += PENALTY_N1;
                }
                else if( runX > 5 )
                {
                    result++;
                }
            }
            else
            {
                finderPenaltyAddHistory( runX + padRun, runHistory );
                padRun = 0;

                if( !runColor )
                {
                    result += finderPenaltyCountPatterns( runHistory, qrsize ) * PENALTY_N3;
                }

                runColor = getModule( qrcode, x, y );
                runX = 1;
            }
        }

        result += finderPenaltyTerminateAndCount( runColor, runX + padRun, runHistory, qrsize ) * PENALTY_N3;
    }

    /* Adjacent modules in column having same color, and finder-like patterns */
    for( int x = 0; x < qrsize; x++ )
    {
        bool runColor = false;
        int runY = 0;
        int runHistory[ 7 ] = { 0 };
        int padRun = qrsize; /* Add white border to initial run */

        for( int y = 0; y < qrsize; y++ )
        {
            if( getModule( qrcode, x, y ) == runColor )
            {
                runY++;

                if( runY == 5 )
                {
                    result += PENALTY_N1;
                }
                else if( runY > 5 )
                {
                    result++;
                }
            }
            else
            {
                finderPenaltyAddHistory( runY + padRun, runHistory );
                padRun = 0;

                if( !runColor )
                {
                    result += finderPenaltyCountPatterns( runHistory, qrsize ) * PENALTY_N3;
                }

                runColor = getModule( qrcode, x, y );
                runY = 1;
            }
        }

        result += finderPenaltyTerminateAndCount( runColor, runY + padRun, runHistory, qrsize ) * PENALTY_N3;
    }

    /* 2*2 blocks of modules having same color */
    for( int y = 0; y < qrsize - 1; y++ )
    {
        for( int x = 0; x < qrsize - 1; x++ )
        {
            bool color = getModule( qrcode, x, y );

            if( ( color == getModule( qrcode, x + 1, y ) ) &&
                ( color == getModule( qrcode, x, y + 1 ) ) &&
                ( color == getModule( qrcode, x + 1, y + 1 ) ) )
            {
                result += PENALTY_N2;
            }
        }
    }

    /* Balance of black and white modules */
    int black = 0;

    for( int y = 0; y < qrsize; y++ )
    {
        for( int x = 0; x < qrsize; x++ )
        {
            if( getModule( qrcode, x, y ) )
            {
                black++;
            }
        }
    }

    int total = qrsize * qrsize; /* Note that size is odd, so black/total != 1/2 */
    /* Compute the smallest integer k >= 0 such that (45-5k)% <= black/total <= (55+5k)% */
    int k = ( int ) ( ( labs( black * 20L - total * 10L ) + total - 1 ) / total ) - 1;
    result += k * PENALTY_N4;
    return result;
}


/* Can only be called immediately after a white run is added, and */
/* returns either 0, 1, or 2. A helper function for getPenaltyScore(). */
static int finderPenaltyCountPatterns( const int runHistory[ 7 ],
                                       int qrsize )
{
    int n = runHistory[ 1 ];

    assert( n <= qrsize * 3 );
    bool core = n > 0 && runHistory[ 2 ] == n && runHistory[ 3 ] == n * 3 && runHistory[ 4 ] == n && runHistory[ 5 ] == n;
    /* The maximum QR Code size is 177, hence the black run length n <= 177. */
    /* Arithmetic is promoted to int, so n*4 will not overflow. */
    return ( core && runHistory[ 0 ] >= n * 4 && runHistory[ 6 ] >= n ? 1 : 0 )
           + ( core && runHistory[ 6 ] >= n * 4 && runHistory[ 0 ] >= n ? 1 : 0 );
}


/* Must be called at the end of a line (row or column) of modules. A helper function for getPenaltyScore(). */
static int finderPenaltyTerminateAndCount( bool currentRunColor,
                                           int currentRunLength,
                                           int runHistory[ 7 ],
                                           int qrsize )
{
    if( currentRunColor ) /* Terminate black run */
    {
        finderPenaltyAddHistory( currentRunLength, runHistory );
        currentRunLength = 0;
    }

    currentRunLength += qrsize; /* Add white border to final run */
    finderPenaltyAddHistory( currentRunLength, runHistory );
    return finderPenaltyCountPatterns( runHistory, qrsize );
}


/* Pushes the given value to the front and drops the last value. A helper function for getPenaltyScore(). */
static void finderPenaltyAddHistory( int currentRunLength,
                                     int runHistory[ 7 ] )
{
    memmove( &runHistory[ 1 ], &runHistory[ 0 ], 6 * sizeof( runHistory[ 0 ] ) );
    runHistory[ 0 ] = currentRunLength;
}



/*---- Basic QR Code information ----*/

/* Public function - see documentation comment in header file. */
int qrcodegen_getSize( const uint8_t qrcode[] )
{
    assert( qrcode != NULL );
    int result = qrcode[ 0 ];
    assert( ( qrcodegen_VERSION_MIN * 4 + 17 ) <= result &&
            result <= ( qrcodegen_VERSION_MAX * 4 + 17 ) );
    return result;
}


/* Public function - see documentation comment in header file. */
bool qrcodegen_getModule( const uint8_t qrcode[],
                          int x,
                          int y )
{
    assert( qrcode != NULL );
    int qrsize = qrcode[ 0 ];
    return ( 0 <= x && x < qrsize && 0 <= y && y < qrsize ) && getModule( qrcode, x, y );
}


/* Gets the module at the given coordinates, which must be in bounds. */
testable bool getModule( const uint8_t qrcode[],
                         int x,
                         int y )
{
    int qrsize = qrcode[ 0 ];

    assert( 21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize );
    int index = y * qrsize + x;
    return getBit( qrcode[ ( index >> 3 ) + 1 ], index & 7 );
}


/* Sets the module at the given coordinates, which must be in bounds. */
testable void setModule( uint8_t qrcode[],
                         int x,
                         int y,
                         bool isBlack )
{
    int qrsize = qrcode[ 0 ];

    assert( 21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize );
    int index = y * qrsize + x;
    int bitIndex = index & 7;
    int byteIndex = ( index >> 3 ) + 1;

    if( isBlack )
    {
        qrcode[ byteIndex ] |= 1 << bitIndex;
    }
    else
    {
        qrcode[ byteIndex ] &= ( 1 << bitIndex ) ^ 0xFF;
    }
}


/* Sets the module at the given coordinates, doing nothing if out of bounds. */
testable void setModuleBounded( uint8_t qrcode[],
                                int x,
                                int y,
                                bool isBlack )
{
    int qrsize = qrcode[ 0 ];

    if( ( 0 <= x ) && ( x < qrsize ) && ( 0 <= y ) && ( y < qrsize ) )
    {
        setModule( qrcode, x, y, isBlack );
    }
}


/* Returns true iff the i'th bit of x is set to 1. Requires x >= 0 and 0 <= i <= 14. */
static bool getBit( int x,
                    int i )
{
    return ( ( x >> i ) & 1 ) != 0;
}



/*---- Segment handling ----*/

/* Public function - see documentation comment in header file. */
bool qrcodegen_isAlphanumeric( const char * text )
{
    assert( text != NULL );

    for( ; *text != '\0'; text++ )
    {
        if( strchr( ALPHANUMERIC_CHARSET, *text ) == NULL )
        {
            return false;
        }
    }

    return true;
}


/* Public function - see documentation comment in header file. */
bool qrcodegen_isNumeric( const char * text )
{
    assert( text != NULL );

    for( ; *text != '\0'; text++ )
    {
        if( ( *text < '0' ) || ( *text > '9' ) )
        {
            return false;
        }
    }

    return true;
}


/* Public function - see documentation comment in header file. */
size_t qrcodegen_calcSegmentBufferSize( enum qrcodegen_Mode mode,
                                        size_t numChars )
{
    int temp = calcSegmentBitLength( mode, numChars );

    if( temp == -1 )
    {
        return SIZE_MAX;
    }

    assert( 0 <= temp && temp <= INT16_MAX );
    return ( ( size_t ) temp + 7 ) / 8;
}


/* Returns the number of data bits needed to represent a segment */
/* containing the given number of characters using the given mode. Notes: */
/* - Returns -1 on failure, i.e. numChars > INT16_MAX or */
/*   the number of needed bits exceeds INT16_MAX (i.e. 32767). */
/* - Otherwise, all valid results are in the range [0, INT16_MAX]. */
/* - For byte mode, numChars measures the number of bytes, not Unicode code points. */
/* - For ECI mode, numChars must be 0, and the worst-case number of bits is returned. */
/*   An actual ECI segment can have shorter data. For non-ECI modes, the result is exact. */
testable int calcSegmentBitLength( enum qrcodegen_Mode mode,
                                   size_t numChars )
{
    /* All calculations are designed to avoid overflow on all platforms */
    if( numChars > ( unsigned int ) INT16_MAX )
    {
        return -1;
    }

    long result = ( long ) numChars;

    if( mode == qrcodegen_Mode_NUMERIC )
    {
        result = ( result * 10 + 2 ) / 3; /* ceil(10/3 * n) */
    }
    else if( mode == qrcodegen_Mode_ALPHANUMERIC )
    {
        result = ( result * 11 + 1 ) / 2; /* ceil(11/2 * n) */
    }
    else if( mode == qrcodegen_Mode_BYTE )
    {
        result *= 8;
    }
    else if( mode == qrcodegen_Mode_KANJI )
    {
        result *= 13;
    }
    else if( ( mode == qrcodegen_Mode_ECI ) && ( numChars == 0 ) )
    {
        result = 3 * 8;
    }
    else /* Invalid argument */
    {
        assert( false );
        return -1;
    }

    assert( result >= 0 );

    if( result > INT16_MAX )
    {
        return -1;
    }

    return ( int ) result;
}


/* Public function - see documentation comment in header file. */
struct qrcodegen_Segment qrcodegen_makeBytes( const uint8_t data[],
                                              size_t len,
                                              uint8_t buf[] )
{
    assert( data != NULL || len == 0 );
    struct qrcodegen_Segment result;
    result.mode = qrcodegen_Mode_BYTE;
    result.bitLength = calcSegmentBitLength( result.mode, len );
    assert( result.bitLength != -1 );
    result.numChars = ( int ) len;

    if( len > 0 )
    {
        memcpy( buf, data, len * sizeof( buf[ 0 ] ) );
    }

    result.data = buf;
    return result;
}


/* Public function - see documentation comment in header file. */
struct qrcodegen_Segment qrcodegen_makeNumeric( const char * digits,
                                                uint8_t buf[] )
{
    assert( digits != NULL );
    struct qrcodegen_Segment result;
    size_t len = strlen( digits );
    result.mode = qrcodegen_Mode_NUMERIC;
    int bitLen = calcSegmentBitLength( result.mode, len );
    assert( bitLen != -1 );
    result.numChars = ( int ) len;

    if( bitLen > 0 )
    {
        memset( buf, 0, ( ( size_t ) bitLen + 7 ) / 8 * sizeof( buf[ 0 ] ) );
    }

    result.bitLength = 0;

    unsigned int accumData = 0;
    int accumCount = 0;

    for( ; *digits != '\0'; digits++ )
    {
        char c = *digits;
        assert( '0' <= c && c <= '9' );
        accumData = accumData * 10 + ( unsigned int ) ( c - '0' );
        accumCount++;

        if( accumCount == 3 )
        {
            appendBitsToBuffer( accumData, 10, buf, &result.bitLength );
            accumData = 0;
            accumCount = 0;
        }
    }

    if( accumCount > 0 ) /* 1 or 2 digits remaining */
    {
        appendBitsToBuffer( accumData, accumCount * 3 + 1, buf, &result.bitLength );
    }

    assert( result.bitLength == bitLen );
    result.data = buf;
    return result;
}


/* Public function - see documentation comment in header file. */
struct qrcodegen_Segment qrcodegen_makeAlphanumeric( const char * text,
                                                     uint8_t buf[] )
{
    assert( text != NULL );
    struct qrcodegen_Segment result;
    size_t len = strlen( text );
    result.mode = qrcodegen_Mode_ALPHANUMERIC;
    int bitLen = calcSegmentBitLength( result.mode, len );
    assert( bitLen != -1 );
    result.numChars = ( int ) len;

    if( bitLen > 0 )
    {
        memset( buf, 0, ( ( size_t ) bitLen + 7 ) / 8 * sizeof( buf[ 0 ] ) );
    }

    result.bitLength = 0;

    unsigned int accumData = 0;
    int accumCount = 0;

    for( ; *text != '\0'; text++ )
    {
        const char * temp = strchr( ALPHANUMERIC_CHARSET, *text );
        assert( temp != NULL );
        accumData = accumData * 45 + ( unsigned int ) ( temp - ALPHANUMERIC_CHARSET );
        accumCount++;

        if( accumCount == 2 )
        {
            appendBitsToBuffer( accumData, 11, buf, &result.bitLength );
            accumData = 0;
            accumCount = 0;
        }
    }

    if( accumCount > 0 ) /* 1 character remaining */
    {
        appendBitsToBuffer( accumData, 6, buf, &result.bitLength );
    }

    assert( result.bitLength == bitLen );
    result.data = buf;
    return result;
}


/* Public function - see documentation comment in header file. */
struct qrcodegen_Segment qrcodegen_makeEci( long assignVal,
                                            uint8_t buf[] )
{
    struct qrcodegen_Segment result;

    result.mode = qrcodegen_Mode_ECI;
    result.numChars = 0;
    result.bitLength = 0;

    if( assignVal < 0 )
    {
        assert( false );
    }
    else if( assignVal < ( 1 << 7 ) )
    {
        memset( buf, 0, 1 * sizeof( buf[ 0 ] ) );
        appendBitsToBuffer( ( unsigned int ) assignVal, 8, buf, &result.bitLength );
    }
    else if( assignVal < ( 1 << 14 ) )
    {
        memset( buf, 0, 2 * sizeof( buf[ 0 ] ) );
        appendBitsToBuffer( 2, 2, buf, &result.bitLength );
        appendBitsToBuffer( ( unsigned int ) assignVal, 14, buf, &result.bitLength );
    }
    else if( assignVal < 1000000L )
    {
        memset( buf, 0, 3 * sizeof( buf[ 0 ] ) );
        appendBitsToBuffer( 6, 3, buf, &result.bitLength );
        appendBitsToBuffer( ( unsigned int ) ( assignVal >> 10 ), 11, buf, &result.bitLength );
        appendBitsToBuffer( ( unsigned int ) ( assignVal & 0x3FF ), 10, buf, &result.bitLength );
    }
    else
    {
        assert( false );
    }

    result.data = buf;
    return result;
}


/* Calculates the number of bits needed to encode the given segments at the given version. */
/* Returns a non-negative number if successful. Otherwise returns -1 if a segment has too */
/* many characters to fit its length field, or the total bits exceeds INT16_MAX. */
testable int getTotalBits( const struct qrcodegen_Segment segs[],
                           size_t len,
                           int version )
{
    assert( segs != NULL || len == 0 );
    long result = 0;

    for( size_t i = 0; i < len; i++ )
    {
        int numChars = segs[ i ].numChars;
        int bitLength = segs[ i ].bitLength;
        assert( 0 <= numChars && numChars <= INT16_MAX );
        assert( 0 <= bitLength && bitLength <= INT16_MAX );
        int ccbits = numCharCountBits( segs[ i ].mode, version );
        assert( 0 <= ccbits && ccbits <= 16 );

        if( numChars >= ( 1L << ccbits ) )
        {
            return -1; /* The segment's length doesn't fit the field's bit width */
        }

        result += 4L + ccbits + bitLength;

        if( result > INT16_MAX )
        {
            return -1; /* The sum might overflow an int type */
        }
    }

    assert( 0 <= result && result <= INT16_MAX );
    return ( int ) result;
}


/* Returns the bit width of the character count field for a segment in the given mode */
/* in a QR Code at the given version number. The result is in the range [0, 16]. */
static int numCharCountBits( enum qrcodegen_Mode mode,
                             int version )
{
    assert( qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX );
    int i = ( version + 7 ) / 17;

    switch( mode )
    {
        case qrcodegen_Mode_NUMERIC:
           {
               static const int temp[] =
               {
                   10, 12, 14
               };
               return temp[ i ];
           }

        case qrcodegen_Mode_ALPHANUMERIC:
           {
               static const int temp[] =
               {
                   9, 11, 13
               };
               return temp[ i ];
           }

        case qrcodegen_Mode_BYTE:
           {
               static const int temp[] =
               {
                   8, 16, 16
               };
               return temp[ i ];
           }

        case qrcodegen_Mode_KANJI:
           {
               static const int temp[] =
               {
                   8, 10, 12
               };
               return temp[ i ];
           }

        case qrcodegen_Mode_ECI:
            return 0;

        default:
            assert( false );
            return -1; /* Dummy value */
    }
}
